<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>实验4：网页计算器。</title>
</head>
<body>
<p>整数1：<input id="num1" type="text"></p>
<p>整数2：<input id="num2" type="text"></p>
<p>
    <input type="button" value="相加" onclick="calc(add)">
    <input type="button" value="相减" onclick="calc(sub)">
    <input type="button" value="相乘" onclick="calc(mul)">
    <input type="button" value="相除" onclick="calc(div)">
</p>
<p>结果:<input id="result" type="text" readonly></p>
</body>
<script type="text/javascript">
    /**
     * @Description: 
     * @author 朱志文
     * @date 2021/10/8 
    */
    function calc(func) {
        var result = document.getElementById('result')
        var num1 = parseInt(document.getElementById('num1').value);
        var num2 = parseInt(document.getElementById('num2').value);
        if (isNaN(num1 || isNaN(num2))) {
            alert("请输入数字")
            return false;
        }
        result.value = func(num1, num2)
    }
    function add(num1, num2) {    // 加法
        return num1 + num2;
    }
    function sub(num1, num2) {    // 减法
        return num1 - num2;
    }
    function mul(num1, num2) {    // 乘法
        return num1 * num2;
    }
    function div(num1, num2) {    // 除法
        if (num2 === 0) {
            alert('除数不能为0');
            return '';
        }
        return num1 / num2;
    }
</script>
</html>